Incandescent lamp.



R. JACOBY.

INCANDESCENT LAMP.

APPLICATION FILED IuIIEz. I9I4.

l 9 1 54,5 l 4@ Pa'ented Sept. 2l, 1915 UNTTED sTATEs PATENT onirica.

RICHARD JACOBY, 0F BERLIN, GERMANY, ASSIGNOR TO GENERAL ELECTRICCOMPANY.

" A CORPORATION OF NEW YORK.

INCANDESCENT LAMP.

Specification of Letters Patent.

Patented Sept. 21, 1915.

Application led .Tune 27, 1914. Serial No. 847,715.

T0 all 'whom it may concern Be it known that I, RICHARD JACOBY, asubject of the King of Prussia, residing at Berlin, Germany, haveinvented certain new and useful Improvements in Incandescent Lamps, ofwhich the following is a specification.

The present invention relates to incandescent lamps and particularly tolamps in which a metal filament is\operated in an envelop containing agas.

It is the function of the gas to reduce the vaporization of the filamentand thus to enable it to be operated at a higher temperature. The lowheat conductivity of the heavier 'rare gases of the atmosphere, forexample, argon renders their use in gasfilled lamps advantageous. It hasbeen found, however, that in lamps filled with rare gases the film ofmaterial deposited on the bulb is more opaque than in nitrogenfilledlamps. Lamps filled with these rare gases also are subject to arcing ata lower temperature than lamps filled with nitrogen. In accordance withthe present invention these drawbacks are overcome without substantialsacrifice of the low heat losses of the rare gases by adding a smallamount of nitrogen.

The accompanying drawing shows somewhat diagrammatically, anincandescent lamp illustrating one form commonly employed when a gasfiller is provided.

This lamp comprises an elongated envelop 1, in which is mounted a coiledfilament 2 vwhich commonly consists of tungsten, although otherrefractory metals also may be used. The diameter of the glower should beso chosen that it may be operated at excessively high tempera-tures fora good commercial life of the lamp. The increased diameter decreases theproportionate convection and conduction losses so that the filament mayemit light at an efficiency higher than it would have in a'vacuum ifoperated so as to have the same useful life. Coilin the filamentin aclose spiral gives the e ect of `an increased diameter. The filament isattached either by welding or mechanically to supporting wires 3 and 4,which project into the globe to locate the filament neark the lower end.Electrical energy is supplied by'leading-in conductors 5 and 6 sealedinto a stem 7'. in the usual Well understood manner.

The lamp is filled with a mixture of a rare gas or gases and nitrogenhaving a pressure measured when the lamp is cold, of about 400 mm. ofmercury or as low as about 100 mm., but while the higher range ofpressures is preferable the pressure should not be so high'as toendanger the bulb when the filament is heated. It is the functionof thisgaseous atmosphere to: reduce the tendency of the filament to vaporizeand also to carry away by convection currents l the small amount ofvapor which is inevitably pro` duced. The gas can suppress but notentirely prevent vaporization of the filament.

Although the lamp is so constructed that the vaporized material isdeposited near the upper end of the globe where it will not obstruct thelight, in time some of the material may be deposited near enough to thefilament to cut olf the light. When using the rare gases of theatmosphere, for example, argon, and krypton which are extremely in ertchemically and for this reason are known also as the noble gases, thefilm of vaporized metal is black and opaque as the deposited metalremains chemically uncombined. 1

Experiments have shown that when only a very small amount of nitrogen isadded to the argon or other rare gas filling that the deposit on thewalls of the globe assumes a lighter color and obscures less light. Thislight colored deposit has been found in the tungsten lamp to be anitride of tungsten. This action takes place even when the amount ofnitrogen is very small, for example, one-tenth of one per cent. A smallamount of nitrogen does not materially reduce the heat conductivity, asthis is proportional to the relative amounts of argon and nitrogenpresent. Of course, in some cases greater amounts of nitrogen may beused, say up to 10% or even more, the heat con` ductivity beingcorrespondingly higher. The presence of nitrogen also has been found toreduce the arcing to a surprising extent, the discharge voltageincreasing rapidly with even a small nitrogen content instead of beingproportional to the nitrogen content as might be expected. Evena smallpercentage of nitrogen raises the dischargevoltage to the valuecharacteristic of pure nitrogen.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. The combination of an envelop, a gloWer of refractory metal mountedtherein, means for supplying energy thereto, and a mixture of argon and'nitrogen surrounding saidv lower. Y

2. he combination of an envelop, a tungsten filament mounted therein,means for supplying energy thereto, ami gaseous mixture consistinglargely of argon and a small amount of nitrogen surrounding saidEla-ment.

3. An incandescent lamp, comprising a globe, a tungsten lament locatedtherein, currentconductors for said filament, and a gas filling atrelatively consideralile pres sure for said globe, comprisingnitrogenand argon.

4. An incandescent lamp comprising a."

transparent envelop, a gaseous lling .comprising argon and about 0.1% to10% of nitrogen in said envelop, and a tungsten glower thereinproportioned in size to operate at an efficiency higher than theefficiency saidL gloWer would have in a vacuum if operated so as to havethe same useful life.

In Witness whereof, I have hereunto set my hand this 11th day of J une,1914.

RICHARD J ACOBY.

Viitnesses D. KARL NEY, ERNST FRIEDERIGH.

